[Numpy-discussion] Fortran binary files and numpy/scipy

[Nils Wagner]

On Mon, 02 Feb 2009 14:07:35 -0600
  Ryan May <rmay31@gmail.com> wrote:
> Nils Wagner wrote:
>>>> Is this a 64-bit problem ?
>>>>
>>> I don't know if it's a 64-bit problem per-se, so much as 
>>> a disagreement between
>>> fortran and numpy.  Numpy is making the size of the 
>>> integer fields 8 bytes, while
>>> in Fortran, they're only 4 bytes.  When constructing 
>>> your dtype, use np.int32 or
>>> '<i4' for your type for the integer fields, and see if 
>>> that fixes it.
>>>
>> 
>> dt = 
>> np.dtype([('isize','int32'),('irow','int32'),('icol','int32'),('value','float')])
>> 
>> 
>>>>> a
>> array([(16, 0, 11, 1.2549267404367662e-321),
>>         (1081065472, 16, 0, 7.9050503334599447e-323),
>>         (12, 253, 0, 3.4485523805914514e-313),
>>         (0, 16, 0, 5.3474293932967148e-312),
>>         (0, 1079312384, 16, 3.3951932655444357e-313), 
>>(0, 
>> 14, 251, 62.0),
>>         (16, 0, 16, 3.1829936864479085e-313),
>>         (250, 0, 1078525952, 7.9050503334599447e-323),
>>         (16, 0, 16, 1.2302234581447039e-321),
>>         (1078231040, 16, 0, 7.9050503334599447e-323),
>>         (17, 248, 0, 3.4484552433329538e-313),
>>         (0, 16, 0, 5.2413296037731544e-312),
>>         (0, 1077805056, 16, 3.3951932655444357e-313), 
>>(0, 
>> 19, 246, 27.0),
>>         (16, 0, 16, 4.2439915819305446e-313),
>>         (245, 0, 1077411840, 7.9050503334599447e-323)],
>>        dtype=[('isize', '<i4'), ('irow', '<i4'), 
>>('icol', 
>> '<i4'), ('value', '<f8')])
>> 
> 
> Maybe on 64-bit machines, the number of bytes is 64-bits 
>instead of 32 (see the
> fact that the first 12 bytes of the file are 16 0 11. 
> Try:
> 
> dt =
> np.dtype([('isize','int64'),('irow','int32'),('icol','int32'),('value','float')])
> 
> Ryan
> 

Strange

>>> a
array([(16, 11, 254, 254.0), (16, 16, 0, 
5.3686493512014268e-312),
        (4638566878703255552, 16, 0, 
7.9050503334599447e-323),
        (1082331758605, 0, 1079312384, 
7.9050503334599447e-323),
        (16, 14, 251, 62.0), (16, 16, 0, 
5.3049894774872906e-312),
        (4632233691727265792, 16, 0, 
7.9050503334599447e-323),
        (1069446856720, 0, 1078231040, 
7.9050503334599447e-323),
        (16, 17, 248, 35.0), (16, 16, 0, 
5.2413296037731544e-312),
        (4629137466983448576, 16, 0, 
7.9050503334599447e-323),
        (1056561954835, 0, 1077608448, 
7.9050503334599447e-323),
        (16, 20, 245, 24.0)],
       dtype=[('isize', '<i8'), ('irow', '<i4'), ('icol', 
'<i4'), ('value', '<f8')])